The present invention relates to fluid separators for petroleum wells and more particularly to a downhole gas and liquid separator system and method.
Liquids are substantially incompressible fluids while gases are compressible fluids. The production fluid in an oil or gas well is generally a combination of liquids and gases. In particular, the production fluid for methane production from a coal formation includes the gas and water. Pumping such production fluid is difficult due to the compressibility of the gas. Compression of the gas reduces the efficiency of the pump and the pump can cavitate, stopping fluid flow. Downhole gas and liquid separators separate the gas and liquid in the production fluid at the bottom of the production string, before pumping the liquid up the production string, and thereby improve the efficiency and reliability of the pumping process. In some cases, the waste fluids from the production fluid may be reinjected above or below the production formation, eliminating the cost of bringing such waste fluids to the surface and the cost of disposal or recycling.
U.S. Pat. No. 5,673,752 to Scudder et al. discloses a separator that uses a hydrophobic membrane for separation. U.S. Pat. No. 6,036,749 to Ribeiro et al., U.S. Pat. No. 6,066,193 to Lee and U.S. Pat. No. 6,382,317 to Cobb disclose powered rotary separators. U.S. Pat. No. 6,155,345 to Lee et al. discloses a separator divided by flow-through bearings into multiple separation chambers.
Prior known downhole pump or separator systems have included shrouds around the pump or separator to filter production fluid before flow into the inlet port. The porous section or screen of these shrouds extends below the inlet port. Often these shrouds have an impermeable or solid section above the screen that traps gas at the top of the shroud and causes gas lock of the pump.
A downhole gas and liquid separator system includes means for pumping and a shroud around the means for pumping. The means for pumping has a cone, a nipple, a pump, a rotary separator and a motor respectively connected in descending order from the tubing string of a well. The shroud has a porous section extending downwardly from the cone, and an impermeable section extending downwardly from the porous section with a motor adapter at the lower end. The means for pumping includes at least one inlet port and the top of the impermeable section is located above the inlet port. The separator system is located above the bottom of the well casing so that production fluid flows up the casing to the upper end of the impermeable section, through the porous section and then flows down to the inlet port, releasing gas as the flow changes from up to down and during the downwards flow. A downhole method of separating gas and liquid from production fluid includes directing production fluid upwards between the casing and the impermeable portion, directing the production fluid over the upper end of the impermeable portion, and directing the production fluid downwards to the inlet port.